<!doctype html>
<html>
  <head>
    <title>fractions invalid</title>
    <meta charset="utf-8"/>
  </head>
  <body>

    <!-- Testing invalid fractions -->
    <math>
      <mfrac><mn>1</mn>bad<mn>2</mn></mfrac>
    </math>
    <math>
      <mfrac>
        <mrow><mi>x</mi><mo>+</mo>bad<mn>1</mn></mrow>
        <mrow><mi>x</mi><mo>+</mo><mn>2</mn></mrow>
      </mfrac>
    </math>

  </body>
</html>